Apparatus for purifying pulp stock



July 17, 1934. s UNDBERG 1,967,032

APPARATUS FOR PURIFYING PULP STOCK original Filed March 18, v1930 ATvroRNEY UNTED STATES PTET Patented `iuly 17, 1934 APPARATUS FOR PURIFYING PULP STOCK FFIC corporation of New Jersey v Application March 18,

1930, Serial No. 436,790

Renewed November 15, 1932 6 Claims.

y This invention relates to mechanism for purifying liquids by the action of centrifugal forces. While the invention is applicable to liquids in general, it pertains more particularly to aqueous suspensions of fibrous materials such as cellulosic bers. Suspensions of this type include pulp stock made from wood, old paper, rags, jute, 'bagassa and a number of other materials. Such pulp is liable to contain therein specks'of foreign 10 matter which are objectionable in paper or other finished product which may be made from the pulp. It is an object of the invention to provide mechanism for purifying ther pulp through centrifugal action, the apparatus being designed to handle the pulp in a novel manner and to separate the particles of foreign matter from the pulp eiciently. It is a further object of the invention to provide apparatus which is comparatively compact in structure so as to econorrize in floor space, and to be capable of easy cleaning after a run. In centrifuging pulp stock for the purpose of separating out the particles of foreign matter which may be present, it is desirable to form within the centrifuge one or more pools of stock against the wall of the rotating drum.. In-

wardly extending ribs or barriers are preferably supplied over which the pulp must flow in a thin stream, these ribs tending to break up fiber bunches and to promote an even distribution of j `3,0 the pulp to the aqueous medium.

According to the present invention a drum of a centrifuge is provided consisting of a pair of coaxial drums, one within the other. Provision is made for introducing a constant stream of pulp f into an end of the inner drum. This stock flows along the wall of the drum, being held against the wall by the centrifugal action resulting from the rotation of the centrifuge. At the opposite end of the drum the stock is permitted to flow Y, 40 over an inwardly extending rim, the escaping stock being flung against the wall of the outer drum adjacent to an end thereof. 1n the outer drum the stock flows in an opposite direction to Vthe other end of this drum whence it is dis- ,45 charged into a suitable receptacle.

Y of the drum. It is desirable to regulate the ro- As the fibrous matter is ordinarily tation so as to cause some of the bers in the pulp to form a soft mat against the wall of the drum. This mat is important for the successful operation of the mechanism, since the libres on its surface exert a combing action on the thin stream of pulp iiowing over the mat so as to comb out particles of foreign matter which might otherwise be carried along with the stream. This is especially true Where the foreign matter has a specific gravity only slightly greater than that of the pulp stock. For the formation of such a mat within the drum, the speed of rotation must be regulated Within limits. If the rotation is too slow the stream of pulp washes through without the formation of any mat at all, so that only the denser particles of foreign matter are retainedwithin the drum. If the speed of rotation is too great, the mat packs very densely and is less efficient in combing out specks from the stream of stock passing over it. Owing to the difference in diameter between the two drums constituting the centrifuge embodying the present invention, there is a certain difference of centrifugal action in the two drums which results in a slightly denser packing of the mat in the outer drum than in the inner drum. Thus by proper regulation of the speed of rotation of the centrifuge, this speed depending on the actual diameters of the drums, a relatively'soft matmay be formed on the inner drum to catch the denser particles and to remove at least a portion of the foreign matter from the pulp stream. In the outer drum a slightly denser mat is formed which reaches the particles having a density more nearly eaual to that of the stock, on account of the greater centrifugal effect on the stream of stool?.

in the outer drum. Through proper regulation of the speed of rotation of the centrifuge, this fea ture of construction makes possible more efficient purifying of the pulp stock.

For a more complete understanding of the invention and of the various advantageous features thereof, reference may be had to the description which follows and to the drawing which shows an embodiment of the invention in section on a vertical plane.

Referring to the embodiment of the invention illustrated on the drawing, the centrifuge may comprise an outer drum 10 and an inner drum 11 arranged one within the other for rotation on a central shaft l2. As shown, this shaft may have a vertical axis and may be driven as by a motor 13 or any other suitable driving connection. The inner drum 11 may be supported as by radially extending fins or bridging pieces 14 which connect it to a central member 15 mounted on a hub member 16 which is, in turn, secured to the shaft 12. The outer drum may be supported by a disk-like member 17 secured i to the lower end of the drum, this disk member having a hub portion 18 mounted directly on the shaft 12. The disk member 17 may also have thereon a brake drum 19, cooperating with braking mechanism indicated at 20 by which the cen- 10 trifuge may be quickly stopped kafter the power is turned off.

Pulp may be supplied to the inner drum'at `its upper end through a supply f'pipe'25 which opens into the upper end of the drum. The upper portion of the drum may be provided with a conical or bell-mouth portion 26, with the small end uppermost to receive the incoming A'stream fof stock. An apron 27 may be mounted within the upper end of the drum to deflect stock flowing l into the drum and to conduct such stock outwardly to the wall of the drum. This apron 27 also imparts rotational motion to the stock received from the pipe so that this stock-is deposited against the wall of the inner drum 25 with minimum disturbance. At the lower end of the inner drum is an inturned flange or rib 30. 'I'he presence of this rib causes the stock entering the inner drum to form in a pool against the `wall of the drum until the pool is of suflicient 30 depth to overflow `the flange 30. The overflowing stock is flung from the lip or inner edge -of the flange into :the adjacent rend ofl the outer drum 10 where it is prevented from flowing downwardly by the presence of the' end member v1'?.

The stock in the outer drum thus flows upwardly and overflows an inwardly extending rib'31 adjacent to the upper end of the drum 10. II'his drum is preferably provided witlran enlarged extension 32 atits upper end, a deeper pool being 40 formed in this extension by a lflange 33 which extends inwardly and -is preferably provided with a relatively sharp edge over which the pulp stream may flow. l

`Into the pool of stock which backs up behind the flange 33 extends a skimming ring 34, the

outer edge of the lskimming ring being bent downwardly as at 35. This ring may be conveniently mounted on the upper part of the innerd-rum 11 as by suitable struts 35, the ring being adjustable toward or from Ithe edge of the flange' 33 so as to regulate the clearance between 'the ring and this flange. 'The pulp 'entering the supply pipe 25 flows into the upper end of the'drum l1 and is deflected by the apron'27 against the wall of '55 the drum ll. By proper regulation of the speed of rotation a yrela-tively soft mat of pulp-may be formed within this drum -to catch the heavier particles of foreign matter which may be present in the stream. Those that are not caught by this :80 mat are acted upon by a slightly greater centrifugal force in the larger drum l0 wherel a denser mat-is formed to comb out`V such particles and to deliver the'stream to the deeper pool at the upper extension of lthe drum practically free! frornparm ticles of greater density than the stock. vParticles of lighter density than the 'stockt are caught vby the :skimming ring 34. Thestock in passing over the flanges or ribs 30, 31 and 33 issubjected V-to an vactionthereby whichtends to break up any (0 Wfiber bunches which may be present in 1the stream. The purified stock which flows over the flange 33 is projected outwardly into a suitable channel 4o Yfrom which a'discharge 'pipe 41 leads.

The apparatus may -be conveniently mounted ,5 on a suitable frame' 45, a cover '4S-being provided over the drums. Suitable openings may be provided in the cover 46, these openings being enclosed by lids 47 which are removable to facilitate the cleansing of the drums after a run. For this purpose a stream of water may be projected by means ofa rhose through the openings 47 to wash out the mats of pulp which have been formed against the inner surfaces of the drums Vamid which contain the impurities combed from .the pulp stream.

I claim: Y1. Mechanism' for-purifying pulp stock, comlprlsingza'sha-ft, a pair of nested drums mounted on y'said shaft for rotation therewith, the inner drum being open atone end and having a bell-shaped 9U end .Walla-at the other end with a central opening about the shaft to receive stock to be puried,

a bell-shaped apron mounted on said shaft within said'innerdrurn adjacent to the supply end thereof, and means for guiding a supply stream of stock onto said apron; 'said inner drum also Yhaving an inward flange'at its'open end to maintain a poolv in said inner drum during operation, 'the outer drum being open at both'ends and'project-y ing axially beyond the open end of the inner drum "l to receive liquid therefrom, said outer drum having an inward flange extending inwardly of the Vinner drumand an inward flange atits opposite end'over which liquid may be discharged. 2. Mechanism for'purifying pulp stock, com- L105 prisinga shaft, a pairof nested drums mounted on said 'shaft for rotation, the inner drum being open at one end and having at the other end a bell-shaped Wall with a central opening to receive stock to be purified, a bell-shaped apron mountedi on said shaft within said inner drum adjacent to the supply end thereof, means for guiding a supply stream of stock onto said apron, said inner drum also having an inturned edgeat its open end to. Y maintain apoolv of liquid therein duringoperaf tion, theouter Vdrum being substantially openV at both ends, said outer drum having an Ainward flange adjacent to the open end of the .inner drum and extending'inwardly of said drum, radial sup-..r port members for said 'inner drum extending from"`120 saidapron to the end`wall thereof, and radial 'support' members for the outer drum'extending to vsaid flange from 'said shaft.

3.Apparatus for purifying paper pulp stock, comprising a plurality of nested cylindricall drumsy` rotatable-on a common axis, means in said drums for retaining therein during the operation thereof po'ols of pulpstock, said means including a `-narrowinwardly extending flange at the discharge endl of the inner drum, means for Support-Ik 130 ing said inner'drurn so that its discharge end is within an adjacent end portion of the outer drum and clear therefrom, lsaid flange being-so arranged that stock which flows thereover has a direct unobstructedlflight from the lip thereof to the aidjacent portion of the outer drum, lsaid outer drum having means formaintaining therein during operation a pool'of vpulp stook'with a free surface from'one end of the drum to the other.

4. A method ofwpurifying paper pulp stockf'li which comprises forming-a pair-of nested cylindrical mats of pulp rotating on a common axis,

flowing in one direction over the surface of the inner mat a thin stream of stock with a free surface, discharging said thin stream from the entire' 145 end periphery of 'the inner mat in unobstructed flight to the outer mat, the direction of flight having an axial componentin the direction of flow of the stream over the inner'mat, flowing said streamY in fthe'opposite directionV over the-150 surface of said outer mat and collecting the stock discharged therefrom.

5. A method of purifying paper-pulp stock, which comprises forming a pair of nested cylindrical mats of pulp rotating on a common axis, flowing a thin stream of stock with free surface in one direction over the surface of the inner mat, discharging said thin stream in unobstructed flight from the entire end periphery of the inner mat to the outer mat, the direction of flight having an axial component in the direction of ilow of the stream over the inner mat, flowing said stream with a free surface in the opposite direction over the surface of said outer mat and collecting the stock discharged therefrom.

6. Apparatus for purifying paper-pulp stock, comprising a plurality of nested cylindrical drums rotatable together on a common axis, the inner drum terminating at one end with a narrow inwardly extending flange over which liquid within said inner drum is adapted to ow, said outer drum having at one end a portion extending axially beyond said flanged end of the inner drum and at the other end an inwardly extending flange the lip diameter of which is greater than the external diameter of said inner drum whereby the liquid pool in the outer drum during operation is maintained with a free surface, the flange of the inner drum being so arranged that liquid flowing over said flange during the rotation of said drums has a free unobstructed flight from the lip thereof to the adjacent portion of the outer drum, and means for introducing liquid to be purified into the end portion of the inner drum remote from said flange.

SVEN C. LINDBERG. 

